Engine valves are vital parts of an engine. They control the flow of gases in and out of engine cylinders. Their sealing affects the horsepower, fuel economy, balance and emissions of an engine. The valves reciprocate back and forth in valve guides to open and close intake and exhaust passages which communicate with engine cylinders. Their tapered valve faces contact narrow tapered surfaces in engine heads or blocks, commonly referred to as valve seats to seal the intake and exhaust passages from the cylinders during compression and power strokes of the engine.
If valves do not fit properly in the tapered seats, intake and exhaust passages will not be sealed off during compression and power strokes, causing power losses, reduced fuel economy, rough engine idling and increased pollution. Imperfect sealing also reduces valve and valve seat life by allowing hot exhaust gases, when peak temperatures occur during ignition, to leak and contact valve faces and valve seats. It can also accelerate valve guide wear, causing increased oil consumption.
Imperfect sealing occurs when valve seat runout, ovality and concentricity exceed required tolerances. Measurements of runout, ovality and concentricity have been inconsistent, especially when made by different inspectors. A repeatable apparatus is needed for checking the close tolerances of valve seats and guides during the manufacturing process. The large number of valve seats in an engine requires an improved apparatus which is efficient and easy to use.